Conventionally, feeding bottles are composed of a flask whose opening, which is defined by a neck, can receive a teat. The teat, which can be composed for example of rubber or silicone, comprises in particular a base forming an annulus, bearing on the neck of the feeding bottle.
This teat is generally fixed to the flask by means of a connecting ring that is screwed onto the neck of the flask and, once screwed, tightens the annulus-shaped base of the teat against the edge of the neck of the flask.
This screwing effected by the user requires several movements, and tricky adjustment. This is because the level of tightening of the connecting ring on the flask must be adjusted carefully to allow correct use of the feeding bottle.
This tightening must be sufficient to guarantee the retention of the teat. This retention, which is checked by a standard test, aims to prevent traction exerted on the teat making it possible to remove it. This removal, effected by the child, would obviously give rise to a risk of spillage of the content of the feeding bottle.
The tightening must however not be too great. This is because excessive tightening may in some cases damage these objects by causing shrinkage of the base of the excessively compressed teat, which then passes into the neck of the flask and no longer ensures either the holding of the teat or its sealing. This excessive tightening also gives rise to a risk of damage to the teat.
Moreover, tightening of the teat must also make it possible to allow or not a passage of air between the teat and the flask of the feeding bottle. This is because air must enter the flask as the liquid contained is consumed.
Some feeding bottles are designed so that the air enters the flask between the base of the teat and the neck of the flask. In this case, excessive tightening prevents this entry of air, which is opposed to the correct use of the feeding bottle. On the other hand, insufficient tightening causes excessive entry of air and therefore an excessively high output of the feeding bottle, and a risk of leakage of liquid.
On feeding bottles of more recent design, comprising an independent valve allowing the entry of air into the feeding bottle, the tightening must ensure sealing of the feeding bottle.
In addition, the level of tightening necessary for different teats on the same feeding bottle does not necessarily correspond to the same number of turns for screwing the ring onto the feeding bottle. This is because the tightening must be adapted according to the thickness of the base of the teat, which may vary slightly due to teat manufacturing tolerances and the characteristics of the material used for the teat (rubber, silicone, or any other material).
This question of tightening of the neck of the feeding bottle therefore often poses a problem for the users, and therefore for the designers of the feeding bottles, who are led to develop systems that are complex, expensive and in the end often difficult to use.